#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
//斐波那契数列
void Fibonacci(int n)
{
	if (n <= 2)
		return 1;
	else
		return Fibonacci(n-1) + Fibonacci(n - 2);
}
int main()
{
	int n;
	scanf("%d", &n);
	int ret=Fibonacci(n);
	printf("%d\n", ret);
	return 0;
}